function show() {
    var url = "/BookServlet";
    if (window.XMLHttpRequest)
        req = new XMLHttpRequest();
    else if (window.ActiveXObject)
        req = new ActiveXObject("Microsoft.XMLHTTP");
    if (req) {
        req.open("post", true);
        req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
        req.onreadystatechange = complete;
        req.send(null);
    }
}

function complete() {
    if (req.readyState == 4) {
        if (req.status == 200) {
        }
    }
}